Selecting GreenHouse Foundation (Detailed Guide)

Most of the Greenhouse Planters ignore the importance of FOUNDATION for a GREENHOUSE. BUT mark my words!

A Perfect foundation leads to a Perfect Greenhouse & a poor Greenhouse foundation leads to lousy Greenhouse!

Still not convinced! of course!

Let’s take a deep dive into the details of the GREENHOUSE FOUNDATION and understand why it is worth learning about the greenhouse foundations before you start building your own greenhouse.

Whenever you are building yourself a GREENHOUSE, the first thing which you have to choose is the greenhouse foundation. Greenhouse foundation is actually the base of the greenhouse on which the entire structure of the greenhouse stands.

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Greenhouse Foundation serves the following purposes:

  1. Greenhouse Foundation Anchors the greenhouse Frame to the ground. Proper anchoring of the frame is very important for a perfect greenhouse because it will hold your greenhouse during hash environments, like strong winds and during heavy rain and snowfall. If your greenhouse foundation is weak then definitely your greenhouse frame will not be properly anchored and even moderate winds can blow your entire greenhouse structure away.
  2. Your Greenhouse Foundation is actually the floor of your greenhouse. It should be strong and rigid along the edges. It should also have a proper growing area for planting ( Either use raised beds or plant directly into the soil, I prefer raised beds). Furthermore, your greenhouse foundation should have designated space for support benches and shelves.
  3. The greenhouse foundation also serves as insulation, to stop the heat/cold seeping into the greenhouse from the ground. You should properly insulate your greenhouse foundation so that there is no heat exchange with the ground. ( Note: If you are using the ground below the greenhouse as a thermal mass then you should not insulate the greenhouse foundation).
  4. Greenhouse foundation also serves the purpose of protecting the greenhouse from external pests and insects.
  5. Finally, The foundation of the greenhouse also insulates the greenhouse from bacteria and fungus that might infect the greenhouse plants.

Factors on which the greenhouse foundation depends?

The choice of your greenhouse foundation depends on the following factors:

1. Greenhous Type and style

Depending on the type and style of your greenhouse you should choose your greenhouse foundation. For example, if your greenhouse glazing and frame are heavy then you must build a Concrete Foundation for your greenhouse because it is strong and can easily withstand large weights.

On the other hand, if your greenhouse frame (wooden, PVC or steel) and glazing materials (Polyethylene) are light then you can choose a wooden foundation for your greenhouse. The benefit of a wooden greenhouse foundation is that it is easy and cheap to build.

2. Climate

Climate is one of the most important factors which will limit the choice of the type of greenhouse along with the choice of greenhouse foundation. If your area receives heavy snow, rainfall, and strong winds then for sure you must go with a concrete foundation for your greenhouse. However, if this is not the case, then I would suggest building a wooden foundation for your greenhouse.

3. Greenhouse Site Selection (soil, slope, etc)

Depending upon the characteristics of the ground site which you have selected for your greenhouse you should choose the greenhouse foundation accordingly. For example, if the soil is sloppy and soft then selecting a strong foundation like concrete would be a better choice to go with.

However, if your greenhouse structure is not very bulky then even a wooden foundation would work great and do the job for you.

But, if your greenhouse structure is bulky and your soil is also very soft or sloppy then I will recommend choosing a strong concerted foundation for your greenhouse.

4. Desired Thermal efficiency

If you want your greenhouse to be more efficient then you should go with a concrete foundation. However, if you have a wooden foundation then you can also easily insulate your greenhouse by installing polystyrene sheets along the walls of the greenhouse (These sheets should be at least 1 food deep inside the ground). Installing polystyrene sheets along your greenhouse walls will greatly increase the thermal efficiency of your greenhouse.

5. Budget

This is one of the most important factors affecting the choice of your greenhouse and greenhouse foundation. If are low in budget or if it is your first time in a greenhouse hobby and you want to spend less then definitely I will recommend a wooden greenhouse.

Keep this in mind that if you can easily afford a concrete foundation for your greenhouse then don’t just go with a concrete foundation for your greenhouse. Decide on the other factors and if you think your greenhouse will be fine with a wooden foundation. Then just go with a wooden foundation.

Note: I always prefer the wooden foundation for my greenhouse because they are cheap, easy to build and later at some point if you change your mind you can easily expand or remove your greenhouse totally.

6. Available Material

Nowadays, A large number of greenhouse kits can be found in the local gardening centers or online shops. However, if you live in an area where greenhouse kits are scarce or you have limited options then choose your greenhouse foundation according to the greenhouse that you have bought.

7. Greenhouse Planters Preferences

Personal preference also plays its part in choosing a greenhouse foundation. Some people might prefer a concrete foundation because of its longevity and strength. However, I tend to like a greenhouse with a wooden foundation the most, because: its more DIY, easy to make and it’s also very cost-effective.

GREENHOUSE Foundation: Site Selection:

Before deciding on the type of Greenhouse Foundation you should first decide on the location where you want to build your greenhouse. For example, a location that is properly leveled and comprises of compressed soil will also help in increasing the life span of your greenhouse.

Choosing the Perfect Site for your Greenhouse Foundation:

The first and foremost thing before constructing your greenhouse foundation is the availability of sunlight. The location where you are planning to build your greenhouse should have a long duration of direct sunlight, which means it should not be shaded with trees or nearby buildings.

The second most important consideration before setting up your greenhouse foundation is the accessibility of your greenhouse (Make sure that your greenhouse is easily accessible, so you can easily work in your greenhouse).

The third consideration before starting the greenhouse foundation is the terrain. The land which you are choosing for your greenhouse should be perfectly flat and the greenhouse drainage would be easy.

Your Greenhouse should not be near the trees because trees shade the greenhouse, which is not acceptable. It will also be hard to dig in the ground with roots and further the expansion of roots as the trees grow might damage your greenhouse foundation.

How to anchor Greenhouse Foundation?

Anchoring is the process of fastening your greenhouse foundation to the ground and this is mostly accomplished using ground stakes.

Ground Stakes:

Some of the greenhouses kits and some DIY plans recommend anchoring your greenhouse foundation using ground stakes to secure the greenhouse frame to the ground. This is the easiest and the widely used method by greenhouse planter to anchor their greenhouse to the ground. This method works best if your greenhouse frame and glazing have less weight and the region where you are building your greenhouse gets very little winds and snow.

However, if your frame and glazing is comparatively heavy then it will be at risk of damage because the greenhouse structure will likely settle and wrap over time. I have seen many greenhouses anchored to the ground using ground stakes and I also have seen a few of them blown away by winds. SO! choose wisely.

What Should be the Size of Your Greenhouse Foundation?

The Size of your greenhouse depends on your requirements, available space, budget and the kit size options (if you are building from a kit). The majority of the greenhouse kits come in various sizes and you can choose your size accordingly.

On the other hand, if you are making DIY greenhouse then available space, budget and your growing requirements would the driving factors determining the size of your greenhouse.

If you are building your greenhouse from a kit, You should definitely check the foundation size provided on that Kit and you should build your greenhouse foundation accordingly.

If your greenhouse kit has come with its own floor, make sure that you fasten your greenhouse floor on a stable and leveled foundation.

On the other hand, if you are making your greenhouse from scratch (maybe you are getting ideas from a plan), make sure you double and triple check the greenhouse foundation measurements before starting the construction.


measure twice, cut once!

Rectangular greenhouses are the most popular and the most recommended. If you are planning to make a rectangular greenhouse, then make sure that your greenhouse foundation is a perfect rectangle. I will explain how to check this in detail later in this article.

Note: If you ask my preference on the size of the greenhouse. I would always go with a larger greenhouse. Because with the time you might wanna increase the variety of vegies you wanna grow in your greenhouse. If you have planned ahead and you have built yourself a large greenhouse. You have saved your time, money and manpower that was required for the expansion of your greenhouse.

What materials should you use in the greenhouse foundation?

There are two main kinds of greenhouse foundations.

  1. Wooden Foundation
  2. Concrete (cement) Foundation

For small greenhouses, I would recommend using a wooden foundation. However, if you are planning to go with a large greenhouse then its best to go with a concrete foundation for your greenhouse.

Furthermore, if you are planning to build a greenhouse with glass (or similar heavy material ) as the glazing material then you should definitely go with a concrete foundation for your greenhouse.

Wooden Greenhouse foundation is fairly easy to make and also it’s very cheap, so it works best for a small greenhouse (for family use). However, large greenhouses need a foundation that is more strong and can easily handle the weight of your greenhouse frame and it can also stay strong in harsh winds and heavy snowfalls.

Wooden Foundation for your Greenhouse

Most of the Greenhouse Planters (including Me) prefer a wooden greenhouse foundation because they are fairly easy and fast to make, require less effort, and are fairly inexpensive. It is more of a DIY task! if we compare it to Concrete greenhouse foundation and we Greenhouse Planters love doing DIY stuff.

Wooden Greenhouse Foundation is very suitable if your greenhouse floor area smaller than 8×12 feet. However, if you are using plastic (polyethylene) glazing for your greenhouse, you can easily extend it to 16-20 feet long, provided that the area where you live in doest get harsh winds.

STEPS for building a WOODEN GREENHOUSE Foundation:

  1. Clean the terrain where you are planning to build your greenhouse. Remove all of the rocks and roots from your greenhouse land.
  2. Level the land where you are planning to build your greenhouse. Make sure to press the soil, so the soil gets firm and stiff.
  3. Cover the greenhouse floor with the ground covering sheet (This recommended if you are planning to plant in the raised beds. if you are planning to plant directly into the ground then you should not cover your greenhouse floor with covering sheet). This will prevent weeds from growing into your greenhouse, it will also keep the pest and insects away and it will also insulate your greenhouse.
  4. Level the greenhouse covering sheet correctly, so that the water can easily drain out of the greenhouse. This is very important, you should check by pouring water on the sheet. The water should flow towards greenhouse drainage. There must be no water pockets on your greenhouse covering sheet.
  5. Make the boundary frame from 4×4 inch or 4×6 inch lumber. Use wood that is resistant to decay, like redwood, cedar or cypress. This would be placed on the floor of the greenhouse. It will also mount the frame of your greenhouse.
  6. Screw the frame together, by using 6 inches galvanized steel screw deck, I recommend using 18V cordless drill for this task.
  7. Fasten your greenhouse boundary from into the ground. You can choose the following options for this task. The first two methods are more of a DIY task ( I love DIY), while if you choose the third option you will be needing assistance.
    1. Hammer 2 feet of wooden nails into the ground along the internal side of the boundary frame (2 or 3 feet apart for more strength). Screw these nails with the boundary frame. This will provide more strength to your greenhouse foundation and will keep your greenhouse frame intact in strong winds. It works just fine 🙂
    2. You can also use 2 feet long rebar pieces for fastening your boundary frame into the ground and use clamping brackets to fasten these bars on to the wooden frame. Keep them 2 to 3 feet apart for more strength. You can also drill holes in the boundary frame and hammer rebars into the ground through the holes in the greenhouse boundary frame. You should make sure that the hole and rebar has a tight fit because if it is loose, your greenhouse frame will not be correctly fastened into the ground.
    3. Another method is to make cement posts below each corner of the boundary frame and fasten the frame to the concrete posts. You should buy brackets to fasten your greenhouse frame to the posts.
  8. Install 1 foot of styrofoam sheets along the outer end of the greenhouse boundary frame. This will prevent the heat from escaping from your greenhouse.
  9. Finally, fill the wooden frame with 3 or 4 inches of gravel (crushed stones). The gravels facilitate the drainage of your greenhouse.
  10. One further note, It as a good idea to dig a hole inside the greenhouse near the foundation, where the drainage water goes. This will avoid hydro pressure building up under your greenhouse foundation.

This video Demonstrates A Wooden Frame Greenhouse, Along with a wooden Foundation. Watch this video it will follow you through the entire building of a Greenhouse.

Cement Foundation for your Greenhouse

Depending on the size of the greenhouse (if your greenhouse size is much greater than 8×12 feet) and your personal preference you might decide to go with a concrete foundation for your greenhouse.

Definitely, having a concrete foundation and a concrete floor is much better than a wooden foundation. But this work is much greater for it to be called a DIY project because you will be needing external assistance for this task.

If you are not comfortable with working with concrete, you might consider purchasing your greenhouse base that is already designed for your particular greenhouse kit. They provide you with a preprinted concrete footer that you can just place on the ground and you can fasten your greenhouse to them.

This video is a good example demonstrating the cement greenhouse foundation. For this greenhouse, they have laid a rectangular foundation for their greenhouse. Then they added a brick wall on top of it which serves the purpose of leveling the edges along with making the greenhouse perfectly rectangular. Then on top of it, the greenhouse can be built. Note: if I was building this greenhouse I would have fixed vertical bolts into the concrete around the edges of the wooden wall and the greenhouse structure can then be tightened using Nuts.

Why having a concrete foundation for your greenhouse is better?

  1. Unlike the wooden foundation, the concrete foundation for greenhouses lasts long.
  2. A concrete foundation for a greenhouse provides perfect drainage, provided that the greenhouse floor has a slight slope.
  3. The floor of a concrete greenhouse is very clean and provides firm support for greenhouse benches and raised beds.
  4. A Concrete floor also insulates a greenhouse, which helps in maintaining the greenhouse temperature.
  5. It also protects the greenhouse from insects, pests, and weeds.

STEPS for building a Concrete GREENHOUSE Foundation:

  1. You should place a rebar mesh on the ground, You should also run rebars along with the edges of the greenhouse (Which is around 1 foot dug in the ground). This rebar mesh will prevent the cement from cracking and will increase the overall strength of the greenhouse foundation. However, you can skip adding rebar in the center regions of the greenhouse if you are sure that the ground and gravels at the center of the greenhouse is properly pressed.
  2. pour concrete on the greenhouse area, make sure that the ground is firmly set and gravels are properly pressed on the ground before adding the concrete. A 3-inch height concrete is considered to be enough for a greenhouse. The ends of the concrete should be 1 inch more than the actual length and width of the greenhouse.
  3. You should add 1-foot deep polystyrene insulation along the edges of the greenhouse. This will prevent the outside cold from entering into the greenhouse.
  4. The lower end of your greenhouse floor should direct the water in a proper area outside the greenhouse, where the water can be collected through a drainage pipe. You can also make a ditch and fill it with gravel along the lower end of the greenhouse for water drainage.

Important things to consider for Greenhouse Concrete Foundation

Before you begin building a greenhouse there are some important things about a concrete based greenhouse foundation in order to ensure that you get the best foundation for your greenhouse.

Concrete Greenhouse Foundation Lasts long:

Concrete has been used for building home and structure for many decades now. Over the years the composition of the concrete has gone through numerous changes over the years, however, the majority of the materials are the same.

The best thing about the concrete foundation is that it will last for decades and centuries. If you have a concrete foundation for your greenhouse and if the foundation is built properly then you don’t have to worry about your greenhouse foundation unless you plant to expand or demolish your greenhouse.

The Confusion between Cement and Concrete:

Cement is the most popular construction material and it consists of limestone, silicon, calcium, aluminum, and iron. They are available in the form of the ground powder and when water is added to the power it binds the particles as it dries.

Concrete is basically a mixture of cement, sand and crushed stones when the concrete dries it binds the mixture together and it is capable of supporting a large amount of weight for decades. This makes concrete on the best building material and therefore is an excellent choice for the greenhouse foundation.

You should not let Concrete Dry quickly:

In order to ensure the strength and longevity of your concrete based greenhouse foundation, you should make sure that the concrete dries slowly during the process of hardening.

If the concrete mix is allowed to dry quickly then the final concrete will not be very strong and it will crack easily when a load is applied on to it. Therefore, you should keep the concrete mix hydrated for at least 7 days.

Initially, when the concrete mix is poured on your greenhouse ground, it needs at least 24 hours to become hard enough so it cannot be carried away by the water. Therefore, you should not pour any water on the greenhouse during the first 24 hours. After that, you should keep on pouring water on the greenhouse to keep it moist.

Some of the Important Greenhouse Foundation Concerns to consider:

Here are some of the common concerns regarding greenhouse foundation:

What is the best foundation for your greenhouse?

If you have already decided on the greenhouse that you wanna build but you are confused about choosing the perfect foundation for your greenhouse. Then you can easily decide based on the soil type, terrain (weather it is slopy or not ), local climate conditions and your greenhouse structure.

If your greenhouse is bulky and heavy (for example: heavy frame with glass windows) then I would recommend building a concrete foundation for your greenhouse. However, if your greenhouse structure is lighter (for example: light frame with polyethylene glazing) then you will be just fine with a wooden foundation. You should also consider the size of your greenhouse, if your greenhouse is much larger than 12 feet in length then I would recommend a concrete foundation for your greenhouse.

Besides the greenhouse structure, your local climate conditions are one of the major factors which you should consider for selecting the greenhouse foundation. If in your local area your climate conditions are harsh (strong winds or heavy rainfalls) then I would highly recommend building a concrete foundation for your greenhouse. However, if this is not the case in your area then just build a wooden foundation for your greenhouse.

Furthermore, you should also consider the soil type and the slope of the terrain on which you wanna build your greenhouse. If the soil is very soft and if the land is sloppy then a concrete foundation might be a better option.

Different greenhouse foundation pros and cons?

Both the wooden and concrete foundations have their own pros and cons.

Wooden Greenhouse Foundation Pros:

  • Very user-friendly to work with more of a DIY job.
  • Cost-Effective.
  • It Can easily be removed and expanded
  • Beginner Friendly

Wooden Greenhouse Foundation Cons:

  • It only supports light greenhouse structures.
  • Greenhouse with a wooden foundation cannot withstand harsh climate conditions.
  • Have a very small life (compared to concrete).

Concrete Greenhouse Foundation Pros:

  • Supports heavy greenhouse structures.
  • Greenhouse with the concrete foundation can withstand harsh climate conditions.
  • Have a long life.

Concrete Greenhouse Foundation Cons:

  • Very hard to work with, require specialized skills and manpower. (More than a DIY task).
  • It cannot be removed or expanded easily.
  • Cost ineffective.
  • It requires to much work to build.

How to make sure that the dimensions of the greenhouse are a perfect rectangle?

It is very important to ensure that your greenhouse base is a perfect rectangle. It is very easy to check it, just run a measuring tape along the diagonals of your greenhouse foundations. The two diagonals should have the exact same lengths if it the case then your greenhouse is a perfect rectangle. If not then you have to adjust your greenhouse perimeter walls in order to get a perfect rectangle.

What Happens If you have a weak greenhouse Foundation?

If your greenhouse is bulky and heavy and your greenhouse foundation is weak then the frame of your greenhouse might get deformed. On the other hand, if your greenhouse light but your greenhouse foundation is weak then your greenhouse would be very susceptible to the external climate conditions (for example: moderate winds can blow your greenhouse away).

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